The fraction of filtered urea excretion by the mammalian kidney is lowered by placing the animal on a protein deficient diet. Mechanisms by which the kidney regulates urea excretion to conserve urea nitrogen during protein deprivation are not precisely known. The mechanism by which the urea concentration in papillary tissue may exceed the urine urea concentration is also unknown. Out proposed work will study the effect of adrenal glucocorticoids on the renal regulation of urea excretion. The existence of active urea transport will be sought in vitro tissue slice incubation studies or in renal tissue cultures.